Invasive exotic plant monitoring at Golden Spike National Historical Park: 2021 field season

Abstract

Invasive exotic plant (IEP) species are one of the biggest threats to natural ecosystem integrity and biodiversity. Controlling them is a high priority for the National Park Service. The Northern Colorado Plateau Network (NCPN) selected the early detection of IEPs as one of 11 monitoring protocols to be implemented as part of its long-term monitoring program. This report represents work completed during the 2021 field season at Golden Spike National Historical Park (NHP). On June 24–25, 2021, we recorded a total of six priority IEP species during monitoring at the park. A total of 191 priority IEP patches were detected along 20 kilometers (12.4 miles) of 13 monitoring routes that covered all major roads, trails, and riparian areas. Three additional IEP species were recorded only in transects. The highest densities of IEP patches were recorded along the Hydro 1 and Last Cut drainages, followed by the Residence Service Road, East Tour Road, and Visitor Center Sidewalk Area. Rush skeletonweed (Chondrilla juncea) was the most prevalent priority species, representing 46% of all recorded patches. Field bindweed (Convolvulus arvensis) and Scotch thistle (Onopordum acanthium) constituted most other patches. The notable absence of Russian knapweed (Centaurea repens) represents past control efforts for this species. When compared to 2018, there was a dramatic increase in the number of IEP patches in 2021, driven by rush skeletonweed and field bindweed. More-widespread species monitored in transects were still common, with cheatgrass (Bromus tectorum), crested wheatgrass (Agropyron cristatum), and tumble mustard (Sisymbrium altissimum) present in 84%, 45%, and 36% of all transects, respectively. The network plans to return to Golden Spike NHP for an eighth year of monitoring in 2023.